Characterization of Artisanal Spontaneous Sourdough Wheat
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foods Article Characterization of Artisanal Spontaneous Sourdough Wheat Bread from Central Greece: Evaluation of Physico-Chemical, Microbiological, and Sensory Properties in Relation to Conventional Yeast Leavened Wheat Bread Pavlina Katsi 1, Ioanna S. Kosma 1, Sofia Michailidou 2, Anagnostis Argiriou 2,3 , Anastasia V. Badeka 1,* and Michael G. Kontominas 1,* 1 Laboratory of Food Chemistry, Department of Chemistry, University of Ioannina, 45110 Ioannina, Greece; [email protected] (P.K.); [email protected] (I.S.K.) 2 Centre for Research and Technology Hellas, Institute of Applied Biosciences, 6th km Charilaou-Thermis, 57001 Thessaloniki, Greece; sofi[email protected] (S.M.); [email protected] (A.A.) 3 Department of Food Science and Nutrition, University of the Aegean, 81400 Myrina, Lemnos, Greece * Correspondence: [email protected] (A.V.B.); [email protected] (M.G.K.) Abstract: In the present study, both yeast leavened bread (YLB) and artisanal sourdough wheat bread (SDB) were prepared. The physico-chemical, microbiological, and sensory properties of breads were ◦ Citation: Katsi, P.; Kosma, I.S.; monitored as a function of storage time (T = 25 C). As expected, the titratable acidity (TA) values of Michailidou, S.; Argiriou, A.; Badeka, SDB were higher than those of YLB. The aroma profile of SDB was similar to that of YLB, including A.V.; Kontominas, M.G. classes of compounds such as alcohols, aldehydes, ketones, esters, organic acids, terpenes, and sulfur Characterization of Artisanal compounds; however, the concentrations between the two were different. Aroma deterioration of Spontaneous Sourdough Wheat bread during storage was partly related to the loss of several volatiles. Texture and sensory analysis Bread from Central Greece: showed that SDB was harder, less elastic, but richer in aroma and light sour taste than YLB. Mold Evaluation of Physico-Chemical, growth was apparent when the population of yeasts/molds reached approximately 4 log cfu/g. Microbiological, and Sensory This yeast/mold count was reached on days 4–5 for YLB and day 18 + for SDB. A 16S amplicon Properties in Relation to Conventional Yeast Leavened Wheat meta-barcoding analysis showed that the bacterial profile of SDB was dominated by a single genus, Bread. Foods 2021, 10, 635. https:// (Lactobacillus). Analysis of the eukaryotic load showed that at the genus level, Saccharomyces and doi.org/10.3390/foods10030635 Alternaria were the most abundant genera, independently of the gene sequenced (18S or ITS). Based primarily on mold growth and texture data, which proved to be the most sensitive quality parameters, Academic Editors: Marina Carcea and the shelf life was ca. 4–5 days for YLB and 10 days for SDB. Mike Sissons Keywords: sourdough bread; yeast leavened bread; microbiological; physico-chemical; sensory Received: 27 January 2021 analysis; shelf life Accepted: 12 March 2021 Published: 17 March 2021 Publisher’s Note: MDPI stays neutral 1. Introduction with regard to jurisdictional claims in published maps and institutional affil- Bread is probably the oldest “processed” food product. Carved images of bread fur- iations. naces have been recovered from Memphis ruins in Egypt as soon as 3000 B.C. Ancient Egyp- tians had over 50 different types of cakes, unleavened breads, and bread leavened with beer foam or sourdough [1]. Industrial wheat bread production started at the beginning of the 20th century after the introduction of baker’s yeast as a superior leavening agent to sourdough and brewer’s yeast. Ever since, the use of sourdough in bread production has Copyright: © 2021 by the authors. been largely abandoned until very recently when consumer demand for the consumption Licensee MDPI, Basel, Switzerland. of more natural bakery products with improved sensory properties and an extended shelf This article is an open access article life, has revived the bakery industry’s interest in using sourdough for breadmaking. distributed under the terms and conditions of the Creative Commons According to Ganzle and Gobbetti [2], the advantages of using sourdough in bread Attribution (CC BY) license (https:// making include acidification, improvement of dough properties, improvement of texture, creativecommons.org/licenses/by/ flavor, leavening capacity, delayed staling, and increased resistance to microbial spoilage. 4.0/). Foods 2021, 10, 635. https://doi.org/10.3390/foods10030635 https://www.mdpi.com/journal/foods Foods 2021, 10, 635 2 of 23 Furthermore, sourdough enhances the nutritional value of bread through increasing min- eral bioavailability, reducing the phytate content, lowering the postprandial glucose level, and providing certain exopolysaccharides with prebiotic and anti-staling properties. All the above benefits have been attributed to the lactic acid bacteria and yeasts naturally present in sourdough [3]. The sourdough lactic acid bacteria (LAB) fermentation creates an optimum pH for the activity of the endogenous enzymes (amylases and proteases) and improves bread loaf volume, delays starch retrogradation and bread firming, inhibits ropiness by spore-forming bacteria, and enhances flavor [4]. Sourdough is a mixture of flour and water that is naturally fermented with a symbiotic culture of LAB and yeasts, native to the flour itself, in a multi-day procedure to reach a pH value below 4.5. The levels of LAB in sourdough are 108–109 cfu/g, and the LAB/yeast ratio is generally 100:1 [5]. The most common LAB species found in sourdoughs are Lb. acidophilus, Lb. farciminis, Lb. delbrueckii (obligate homofermentative), Lb. casei, Lb. plantarum, Lb. rhamnosus (facultative heterofermentative), Lb. brevis, Lb. sanfransicencis, and Lb. fermentum (obligate heterofermentative) [6]. The yeast flora of sourdough is more homogenous. Universal sourdough yeasts appear to be Saccharomyces cerevisiae, Candida milleri, or Candida humilis [7]. LAB are mainly responsible for dough acidification and the modification of dough properties, while yeasts are mainly responsible for the production of flavor compounds. The quality of sourdough bread is influenced by the specific microbiota developed in sourdough (starter cultures of LAB and yeasts), flour type (wheat/rye, flour extraction rate), flour/water ratio (dough yield), and process parameters such as initial pH, quantity of sourdough incorporated in dough, time and temperature of fermentation, etc. [5,8]. Specifi- cally, temperature has a substantial impact on the dynamics of the microbial population and the metabolic activity of the microorganisms during fermentation. Homofermentative and facultative heterofermentative lactobacilli such as Lb. fermentum and Lb. plantarum predominate when the fermentation temperature is above 30 ◦C. In contrast, heterofermen- tative lactobacilli such as Lb. sanfranciscensis predominate when the temperature is lower than 30 ◦C[8]. The shelf life of bread (time period within which bread retains its acceptable qual- ity and safety characteristics) is substantially limited due to several deterioration factors, mostly microbial spoilage and texture firming [9]. Fungal growth is the most common path of bread spoilage owed to species of Penicillium and Aspergillus genera. Bread can also be spoiled from bacteria due to high levels of moisture (Bacillus subtilis, Bacillus cereus, Bacillus licheniformis). Likewise, ropy bread is caused by Bacillus subtilis, resulting in the deteriora- tion of bread texture [10]. Microbial spoilage of bread is due to cross-contamination post baking, as all microbiota is destroyed during the baking process [11]. Physico-chemical changes in bread may occur involving texture and flavor dete- rioration, rendering it stale. Staling is characterized by crumb firming mainly due to the retrogradation of the starch polymers and interactions between starch and proteins, crust softening due to the transfer of moisture from the crumb to crust, and finally flavor changes. Such changes are responsible for the disposal of large quantities of bread (8–10%), resulting in considerable economical losses [12–14]. Based on the above, the objectives of this study were (i) to characterize bread prepared using baker’s yeast and artisanal sourdough on a qualitative and quantitative basis using physico-chemical, microbiological, and sensory analyses and (ii) to identify the specific microbiota dominating the sourdough bread. 2. Materials and Methods 2.1. Artisanal Sourdough Preparation Two hundred grams of commercial wheat flour (85% extraction rate) produced by steel roller grinding) at St. George Mills S.A. Ioannina, Greece, were mixed with 2 g of table salt (0.6% w/w) and 200 mL of warm water (30 ◦C) in a bowl. The specific flour with a high extraction rate including a large part of the wheat bran is used to prepare sourdough in most Foods 2021, 10, 635 3 of 23 parts of Greece. The ingredients were mixed using a sterilized spatula until a homogeneous thick batter was formed. Then, the bowl was covered with a hand towel and left overnight to rest at a temperature of 25 ± 1 ◦C. The following day, the dough was kneaded once more after adding 50 g flour and warm water (30 ◦C). This procedure was repeated for an additional 4 days, at which point the dough had matured/risen, forming a large number of holes in its mass and surface, which is a sign of vigorous fermentation activity, and giving off a sour and fresh odor. The mature dough, referred to as “sourdough”, was placed in a mason-type jar and stored in the refrigerator while a part of it was used for bread making. The particular recipe for the preparation of the sourdough was that used in the area of Northern Nafpaktia, central Greece. 2.2. Bread Preparation Two types of bread were prepared; bread leavened with baker’s yeast (control, YLB) and sourdough bread (SDB). Control bread was prepared using 1000 g flour (1/3 wheat flour, 70% extraction rate, and 2/3 whole wheat flour), 700 mL of water, 6 g of salt (0.6% w/w) and 4 g of commercial baker’s yeast (GIOTIS S.A., Athens, Greece) added to the flour mix. The specific flour mixture was used to simulate the flour with an 85% extraction rate used for the preparation of sourdough, given the fact that baker’s yeast works better with flour with a 70% extraction rate.